Characterization of elevated-temperature high strength and decent thermal conductivity extruded Mg-Er-Y-Zn alloy containing nano-spaced stacking faults

A new elevated-temperature high strength Mg-0.6Er-0.6Y-1.2Zn-0.2Mn (at.%) alloy with decent thermal conductivity was developed by semi-continuous casting, solid-solution treatment and hot-extrusion. Two secondary phases, i.e. 18R-long period stacking ordered (LPSO) phase and W phase (Mg₃(Er,Y)₂Zn₃), would be formed in the as-cast alloy mainly due to the alloy component of (Er + Y): Zn = 1: 1 and Er: Y = 1: 1 (at.%). After solid-solution treatment and hot extrusion, the most significant microstructure characteristic formed in as-extruded alloy is numerous nano-spaced basal plane stacking faults (SFs) in all the dynamically recrystallized (DRXed) and un-DRXed grains, which is very rare in the previous reports. The as-extruded alloy exhibits excellent performances from room temperature to 300 °C. The tensile yield strength can be maintained above 300 MPa at 200 °C and above 250 MPa at 300 °C, and the thermal conductivity is 86.0 W/m·K at 300 °C. The superior elevated-temperature strength is mainly related to the formation of the nano-spaced basal plane SFs throughout the whole Mg matrix, the fine DRXed grains with size of ~2 μm, the strongly textured un-DRXed grains with numerous sub-structures, and fine W phase particles as well as LPSO phases.